- Describe how substance abuse disorders are diagnosed
- Describe depressants and the impact of their use
- Describe stimulants and the impact of their use
- Describe opioids and the impact of their use
- Describe hallucinogens and the impact of their use
- Compare and contrast between depressants, stimulants, opioids, and hallucinogens
Substance Abuse Disorders
The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) is used by clinicians to diagnose individuals suffering from various psychological disorders. Substance use disorders are addiction disorders, and the criteria for specific substance use disorders are described in the DSM-5. A person who has a substance use disorder often uses more of the substance than they originally intended to and continues to use that substance despite experiencing significant adverse consequences. In individuals diagnosed with a substance use disorder, there is a compulsive pattern of drug use that is often associated with both physical and psychological dependence.
dependence, tolerance, and withdrawal
Physical dependence involves changes in normal brain and body chemistry leading to symptoms that are not primarily cognitive or emotional in nature. Users develop a tolerance to substances over time and will experience withdrawal upon cessation of the drug’s use.
In contrast, a person who has psychological dependence experiences a cognitive and emotional, rather than physical, need for the drug and may use the drug to relieve psychological distress.
Tolerance is linked to physiological dependence, and it occurs when a person requires more and more of the drug to achieve effects previously experienced at lower doses. Tolerance can cause the user to increase the amount of drug used to a dangerous level—even to the point of overdose and death.
Drug withdrawal includes a variety of negative symptoms experienced when drug use is discontinued. These symptoms usually are opposite of the effects of the drug. For example, withdrawal from sedative drugs often produces unpleasant arousal and agitation. Many individuals who are diagnosed with substance use disorders experience both tolerance and withdrawal symptoms.
Psychological dependence, or drug craving, is a recent addition to the diagnostic criteria for substance use disorder in the DSM-5. This is an important factor because we can develop tolerance and experience withdrawal from any number of drugs that we do not abuse. In other words, physical dependence in and of itself is of limited utility in determining whether or not someone has a substance use disorder (e.g. someone who has a physical dependence on coffee in the morning does not necessarily have a substance use disorder).
Drug Categories
The effects of all psychoactive drugs occur through their interactions with our endogenous neurotransmitter systems. Many of these drugs, and their relationships, are shown in Figure 1. As you have learned, drugs can act as agonists or antagonists of a given neurotransmitter system. An agonist facilitates the activity of a neurotransmitter system, and antagonists impede neurotransmitter activity.
The main categories of drugs are depressants, stimulants, and hallucinogens. You’ll learn more about these types of drugs in the coming pages.
| Class of Drug | Examples | Effects on the Body | Effects When Used | Psychologically Addicting? |
| Stimulants | Cocaine, amphetamines (including some ADHD medications such as Adderall), methamphetamines, MDMA (“Ecstasy” or “Molly”) (MDMA also acts as a mild hallucinogen) | Increased heart rate, blood pressure, body temperature | Increased alertness, mild euphoria, decreased appetite in low doses. High doses increase agitation, paranoia, can cause hallucinations. Some can cause heightened sensitivity to physical stimuli. High doses of MDMA can cause brain toxicity and death. | Yes |
| Sedative-Hypnotics (“Depressants”) | Alcohol, barbiturates (e.g., secobarbital, pentobarbital), Benzodiazepines (e.g., Xanax) | Decreased heart rate, blood pressure | Low doses increase relaxation, decrease inhibitions. High doses can induce sleep, cause motor disturbance, memory loss, decreased respiratory function, and death. | Yes |
| Opiates | Opium, Heroin, Fentanyl, Morphine, Oxycodone, Vicodin, methadone, and other prescription pain relievers | Decreased pain, pupil dilation, decreased gut motility, decreased respiratory function | Pain relief, euphoria, sleepiness. High doses can cause death due to respiratory depression. | Yes |
| Hallucinogens | Marijuana[1], LSD, Peyote, mescaline, DMT, psilocybin, dissociative anesthetics including ketamine and PCP | Increased heart rate and blood pressure that may dissipate over time | Mild to intense perceptual changes with high variability in effects based on strain, method of ingestion, and individual differences | Yes |
- Note that marijuana (cannabis) is most often included as a hallucinogen due to its psychoactive properties, but it can also be classified as a depressant or stimulant. ↵